Line drive counterflow in situ combustion process



Dec. 10, 1963 A. D. RElcHLE 3,113,619

LINE DRIVE cUNTERFLow 1N SITU coMBUsToN PRocEss Filed March 30, 1959 1 e f r ww f` C o o o o o o o o "C" I3" O o o o o o o o o D INVENTOR. A. D. REICHLE BY Wwf?? A T TORNEYS United States Patent O 3,ll3,6l9 LINE DRIVE CQUNTERFLGW EN SITU COMBUSTIN PRCESS Alfred D. Reiclile, Bmiesville, Ghia., assigner to Phillips Petroleum Company, a corporation of Delaware Filed Mar. 30, 1959, Ser. No. 802,855 10 Claims. tCl. 16e-11) This invention relates to a line drive counterilow in situ combustion process for producing hydrocarbons from a gas permeable carbonaceous stratum.

In situ combustion in the recovery of hydrocarbons from underground strata containing carbonaceous material is becoming more prevalent in the petroleum industry. In this technique of production, combustion is initiated in the carbonaceous stratum and the resulting combustion zone is caused to move thru the stratum by either inverse or direct air drive whereby the heat of combustion of a substantial proportion of the hydrocarbon in the stratum drives out and usually upgrades a substantial proportion of the unburned hydrocarbon material.

The ignition of carbonaceous material in a stratum around a borehole therein followed by injection of air thru the ignition borehole and recovery of product hydrocarbons and combustion gas thru another borehole in the stratum is a direct air drive process for effecting in situ combustion and recovery of hydrocarbons from the stratum. In this type of operation the stratum usually plugs in front of the combustion zone because a heavy viscous liquid bank of hydrocarbon collects in the stratum in advance of the combustion Zone which prevents movement of air to the combustion process. To overcome this difculty and to permit the continued progress of the combustion zone thru the stratum, inverse air injection has been resorted to. By this technique, a combustion zone is established around and ignition borehole by any suitable means and air is fed thru the stratum to the combustion zone from one or more surrounding boreholes.

In situ combustion techniques are being applied to tar sands, shale, Athabasca sand and other strata in virgin state, to coal veins by fracturing, and to strata partially depleted by primary and even secondary and tertiary recovery methods.

In conventional counterflow in situ combustion processes, the well spacing is set by the allowable air injection pressure, necessary average air velocity, formation permeability, and well diameter. This invention pertains to a method for obtaining larger well spacings than normally possible, or increased air flow at the normal spacing.

Accordingly, a principal object of the invention is to provide a technique or process of producing a carbonaceous stratum, such as a tar sand or oil sand, which permits a wider well spacing pattern or increased air ilow rates with normal well spacing for any given field or stratum. Another object is to provide a process for propagating an in-line combustion front thru a stratum by inverse air injection past successive lines of wells wherein a portion or all of the hydrocarbon material is burned out between the wells in each line before arrival of the combustion front. Another object is to provide a more etlicient and effective process for producing a carbonaceous stratum by inverse air injection or counterflow technique. Other objects of the invention will become apparent upon consideration of the accompanying disclosure.

Broadly, the process of the invention comprises increasing the effective diameter of air injection wells in a line pattern by burning out hydrocarbon material from the area around each injection well and then extinguishing the tire or combustion zone around these injection wells so as to increase the permeability of an annular section around each well or of a section of stratum extending from well to well, thereby effectively increasing the diameter of the Cir ICC

injection wells and increasing the flow rate of injected air at any given pressure. In the embodiment of the invention wherein the combustion around the injection wells is terminated before burning completely thru from well to well, a carbonaceous bridge is preserved between injection wells for the propagation of the inverse moving combustion front from one line of wells to the other. In the embodiment of the invention wherein burning is effected completely thru the stratum between injection wells, the combustion front is propagated thru the burned out area either by injecting a suitable fuel, such as hydrocarbon oil or gas into the burned out area before arrival of the combustion front from the line of production Wells around which the front is established, or by incorporating in the injected combustion-supporting gas feeding the combustion front, a low concentration of fuel gas such as natural gas, propane, or LPG., the concentration being in the range of about 2 to 4 volume percent.

After burning out the area around each injection well of a first line of injection wells, a combustion zone is established around each well in a line of production wells generally parallel or concentric with the line of injection wells. The combustion front thus established is moved to the vicinity adjacent the injection wells by injecting combustion-supporting gas, such as air, therethru. During the period in which the combustion front is moving from the production wells to the injection wells the carbonaceous material around the wells in a second line of injection wells is burned out preparatory to using these wells for injecting combustion supporting gas to feed the combustion front which has arrived in the vicinity of the rst line of injection wells. Of course, the burn-out around the second and succeeding lines of injection wells may be effected at any time before their use is required as injection wells. The dierent lines of injection wells are located in consecutive rows or lines across the eld which is to be produced and as one line of injection wells is burned out preparatory to use as injection wells, the preceding line of injection wells is passed by the combustion front and is then used as a line of production wells, preferably, with the previous line of production wells being shut in.

A more complete understanding of the invention may be obtained upon consideration of the accompanying schematic drawing in which FIGURE 1 is a plan View showing a parallel in-line pattern illustrating one embodiment of the invention; and FIGURE 2 is a similar plan view of concentric rings of wells illustrating a second embodiment of the invention.

FIGURE 1 shows a well pattern for carrying out a field operation using counterow in situ combustion in accordance with the invention. The pattern shown in FIGURE 1 consists of wells in rows A, B. C, and D. The rows A, B, C, etc., are, preferably, approximately -140 feet apart. The wells in the various rows numbered 11, 12, 13, etc., are preferably between 30 and 40 feet apart. Larger and smaller well and row spacing may be desirable depending upon the character of the stratum. In carrying out this invention, the individual wells in row B are ignited by any suitable method, such as the charcoal pack method, and allowing to burn with air being injected from the wells in row A or C or both or thru wells B in certain strata. The burning around the wells of row B is allowed to progress so that there is a burned out region around each well with a radius in the range of 1 to 5 feet or more. The wells of row B are then shut in and air injection is terminated to cause the fire to die out. This step in the present invention provides a large more permeable region through which air may be injected to carry out the countercurrent process more eiciently. v

The next step in carrying out the present invention comprises igniting the stratum around lall of the wells in s row A and injecting -air thru the Wells of row B to force same lto row A. The wells in row A are ignited by the use of Ia charcoal pack or other means. The burning in the formation between row A and row B is carried out by the counterow process induced by air injected thru wells B with the re traveling from wells A toward wells B with the Wells of row A being used -for production. An alternative method of getting the wells in row A burning to assure that the entire formation from well All to lwell A19 is burning, comprises using the odd numbered `wells in row A as ignition wells and the even numbered wells as air injection wells, or vice versa. This process -is carried on a short time until burning from the ignition wells to the injection wells is comple-ted and then all the wells in row A Iare turned into production wells.

During the time that the re front is moving from row A to row B, the wells of row C are ignited and allowed to burn a short time to insure a burned out zone around each well similar` to that produced around the wells of row B, `after which the wells of row C are closed in and the re allowed to die. As the flame front approaches :the wells of row B, air is injected into the wells of row C, causing the tire vfront to progress through the unburned region between the individual wells of row B. The burn out around wells B may be controlled so that there will be `approximately 20-30 feet of unburned pay formation between each pair of wells in row B. This unburned formation is left intentionally during the initial operation, in accordance with one embodiment of this invention, to provide -a passageway for the fire across the line of wells of row B. After the fiame front passes the wells of row B, each well of row B is turned into a production well and the wells of row A are shut in. This step reduces the distance thru which hydrocarbons have to travel to a production well. The above operation is continued and the wells of row D are ignited to produce a burned out region, in similar manner lto that applied to rows B and D, as this process progresses.

It the burning, say, around each Well in row B initially is continued until the entire area between each pair of wells is connected with burned out formation, it is necessary to inject oil, or Ifuel gas, etc., thru the wells of row B into the adjacent stratum to assure passage of the lire front across this region in going to the second phase of the process, i.e., transferring the injection of air from row B to row C. Bridging the gap between wells of row B may also be accomplished by injecting combustionsupporting gas thru Wells C containing fuel gas in a concentration in the range of about 2 to 4 volume percent.

FIGURE 2 illustrates a field pattern for in situ combustion utilizing a central well 30 and successive rings of wells 32, 34, Land 36, surrounding well 30 and substantially concentric therewith. IIn operating with this type of well pattern, the wells 32 are burned out in the manner described in connection with row B of FIGURE l, after which the lire is eX-tinquished and the stratum is ignited around central well 30 and the wells 32 are then used as air injection wells. As the lire front is moved from central well 30 to wells 32 by inverse air injection, the wells in ring 34 rare burned in the same manner as the wells in row B, or ring 32, to prepare these for air injection when the fire front reaches the vicinity ladjacent wells 32, at which time wells 32 are temporarily shut in until the lire front passes the ring of wells '32, after which the wells in ring 32 are utilized -as production wells. While the fire front is passing thru .the stratum between the wells in ring 32 and those in ring 34, the wells in ring 36 are burned out to prepare them for use as injection wells. The process is then continued to additional outer rings of wells (not shown).

The ignition of the stratum thru any of the wells in the pattern of FIGURE l or of FIGURE 2 may be elected in conventional manner. A preferred method comprises placing a fuel pack such as charcoal briquettes, porous absorbent ceramic pieces (crushed alumina re brick) soa-hed with heavy oil, or a mixture of charcoal and ceramic pieces either soaked with oil or dry, and igniting and burning the fuel pack so as 'to heat up the surrounding stratum; and feeding combustion-supporting gas (air) to the hot stratum either directly thru the ignition borehole or, preferably, thru the stratum from one or more odset boreholes. The stratum may also be ignited by means of one or more gas burners positioned in the ignition borehole adjacent the carbonaceous stratum or by elect-ric heaters disposed in 'a similiar position to heat the adjacent stra-tum, after which the same is contacted with air.

Certain modiiications of the invention will become apparent to those skilled in the art and lthe illustrative details disclosed are not to be construed as imposing unnecessary limitations on the invention.

I claim:

l. A process of recovering hydrocarbons from a permeable combustible carbonaceous stratum penetrated by consecutive lines of wells A, B, and C, said lines of wells being spaced apart substantially uniformly in the given order, which comprises igniting and burning out carbonaceous material around the wells in line B; thereafter terminating the lcombustion around the wells in line E; igniting said stratum around the wells in line A; injecting combustion-supporting gas thru the wells in line B so as to force same to the resulting combustion zone around the wells in line A and to cause said zone to move to the vicinity adjacent the wells in line B; recovering produced liuids thru the wells in line A while said Zone is moving toward the wells in line B; before said combustion zone reaches the wells in line B, igniting and burning out carbonaceous material ladjacent the wells in line C; terminating combustion `around the wells in line C; and when said combustion Zone reaches the vicinity adjacent the wells in line B, and after terminating the combustion around the wells in line C, closing the wells in one of lines A and B and injecting combustion-supporting gas thru the wells in line C so las to feed the combustion zone adjacent the wells in line B and move same toward the wells in line C.

2. The process of claim l wherein the yburning around the wells in line B is terminated before burning out all of the |area between individual wells so that a bridge of carbonaceous material remains between said individual wells for propaga-ting the combustion zone past the wells in line B toward the wells in line C.

3. The process of claim 1 wherein the burning around wells in line B is completed between said wells and the combustion zone is moved thru the burned out area by including sufficient fuel gas in a concentration inthe range of 2 to 4 volume percent inthe combustion supporting gas injected thru the wells in line C to move said combustion zone therethru to the carbonaceous material intermediate the wells in line B and in line C.

4. The process of claim 1 wherein the stratum between the wells of line B is burned thru land sufficient fuel is deposited in the burned out area 4between wells by injecting `fuel lthru the wells of line B, before the combustion zone arrives from wells of line A, to supply fuel for moving the combustion zone past the wells of line B into unburned stratum.

5. The process of claim 1 wherein said lines of wells comprise three rows of wells.

6. The process of claim 1 wherein said lines of wells comprise three concentric rings of wells.

7. The process of claim l wherein combustion is initiated around -alternate Wells in line A and burn-out is effected by driving the resulting combustion zone across to the `adjacent wells by feeding combustion-supporting gas thereto thru wells in line A.

8. The process of claim 7 wherein said combustion is driven to said 'adjacent wells by injecting combustion supporting gas thru the remaining alternate wells in line A and producing thru first said alternate wells.

9. The process of claim l wherein wells in line B are References Cited in the le of this patent UNITED STATES PATENTS 2,793,696 Morse May 28, 1957 6 Simm et a1. May 28, 1957 Parker Apr. 7, 1959 Parker June 2, 1959 Crawford Aug. 11, 1959 `Campion etal. Aug. 25, 1959 Herzog Sept. 29, 1959 Hurley Nov. 1, 1960 Parker May 1, 1962 

1. A PROCESS OR RECOVERING HYDROCARBONS FROM A PERMEABLE COMBUSTIBLE CARBONACEOUS STRATUM PENETRATED BY CONSECUTIVE LINES OF WELLS, A, B, AND C, SAID LINES OF WELLS BEING SPACED APART SUBSTANTIALLY UNIFORMLY IN THE GIVEN ORDER, WHICH COMPRISES IGNITING AND BURNING OUT CARBONACEOUS MATERIAL AROUND THE WELLS IN LINE B; THEREAFTER 